Heretofore, quaternary ammonium salts have been used for various applications as cationic surfactants. Some of them are known to have strong microbicidal activities. Among them, an alkyldimethylbenzyl ammonium chloride (benzalconium chloride) is utilized in a wide range of fields by virtue of its excellent microbicidal effects (the carbon chain length of the alkyl group is mainly from C.sub.12 to C.sub.14).
On the other hand, developments have been carried out for polymer compounds having microbicidal activities. In particular, an attempt has been made to produce a high molecular weight product by e.g. polymerization of a monomer having a substituent containing a quaternary nitrogen such as an ammonium salt or a pyridinium salt. Specific examples include an acrylic polymer having quaternary ammonium groups as ester residues (Japanese Unexamined Patent Publication No. 6394/1978), a polystyrene derivative having quaternary ammonium groups as substituents on benzene rings (Japanese Unexamined Patent Publication No. 246205/1986), a polyvinylpyridine derivative having pendant pyridinium groups (Japanese Unexamined Patent Publication No. 310803/1988) and a polymer having benzyl ammonium or benzyl pyridinium groups in its side chains (Japanese Unexamined Patent Publication No. 26610/1989).
However, the above-mentioned low molecular weight type quaternary ammonium salts are limited in their applications for reasons such that they have foaming properties in their aqueous solution systems, they are inferior in the thermal stability, or their absorptivity to various material components is remarkable, or the effective ingredients are likely to be discharged outside or tend to separate or sediment inside so that the microbicidal and algaecidal activities deteriorate. Further, conventional polymer-type microbicides containing quaternary nitrogen in their side chains have had a problem such that the activities deteriorate as compared with low molecular weight compounds or totally extinct, so that the microbicidal activities are not necessarily adequate.